Project Description

Overview

During the 2012 floods, the existing concrete invert to a bridge on the River Culm had perished and the retaining wall had partially collapsed – which had the potential to cut off a vital road into a neighbouring village.

Due to the location and the river’s existing habitat, the Environment Agency stipulated a solution that would benefit the habitat while providing a robust repair able to withstand future flooding.

Challenge

To be able to undertake the repairs in dry conditions, we first had to dam and pump the river water through 900mm diameter pipe, and then shore up the retaining wall to prevent further collapse.

We designed a scheme that used 1.5 tonne boulders cast into a 500mm think fibre reinforced concrete slab. We formed shuttering and cast concrete walls cast around the perimeter of the invert slab to prevent loss of fill material, future undermining and possible collapse. We then filled the invert with dredged shingle that had built up downstream, leaving just 300mm of the boulders showing.

To reduce the potential for pollution and impact of contamination, we added special additives to the concrete. We also kept a keen eye on the weather conditions, to monitor river levels and flood risks.

Results

Thanks to the way in which the boulders directed the currents, we were able to create a safe haven for the wildlife living in and around the river. In terms of the collapsed wall, we rebuilt a 3.5-metre high section using stone that matched the existing bridge parapets.

Quick facts:

Client: Devon County Council
Value: £40,000
Project type: Bridges & Structures
Duration 5 weeks